In Figure 6, each bin is wide except for low cone angles
where there are fewer data points. The P4 (16-32 mHz) and P5
(32-64 mHz) events occur more often when the IMF cone angle
is low.
It is especially clear for the P5 events. The P2 events (4-8 mHz)
behave oppositely and occur most often when is high. The
normalized occurrence rate for P3 appears to be a mixture of the results
for higher-frequency and lower-frequency waves.